This invention relates to determination of filter loading and more particularly to the use of microwave sensing to determine filter loading.
In many realms there is a need for accurate sensing of the amount of material that has been captured by a filter. An example is the need to determine filter loading of soot on a diesel particulate filter (DPF). The amount of loading on a diesel particulate filter must be known in order to determine appropriate conditions for start-up of regeneration as well as monitoring conditions to determine when complete regeneration has been achieved. The level of loading is important in this context because regeneration of a DPF is often through an uncontrolled burn in which soot is ignited by the presence of free oxygen and a combustion wave is generated through the filter. Under certain conditions, it is possible that regeneration will produce temperatures that are very high resulting in large thermal stresses that can result in limited fatigue life of the filter and ultimately its destruction. Thus, the level of soot loading is important for successful filter regeneration.
It is well known that there are several methods for determining the loading of a filter. The most commonly investigated method is by measurement of the pressure drop across the filter. This method can be combined with expert systems that calculate the amount of soot that has been captured through a cumulative calculation of soot production through an engine.
An object of the present invention is the application of microwave technology to the determination of the status of loading of traps or filters.